DEGRADATION OF CHLOROETHENES IN AQUEOUS SOLUTION BY ULTRASOUND

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1 DEGRADATION OF CLOROETENES IN AQUEOUS SOLUTION BY ULTRASOUND V. Sáez,, M. D. Esclapez,, P. Bonete,, E. Marchante, J. González-García García,, D. Walton, O. Louisnard

2 SONOCEMICAL DEGRADATION OF ALOCOMPOUNDS AN OVERVIEW Chlorinated organocompounds are usually used as industrial solvents: C 4, C 3, C 2 4, C 2 3, among others, withspread environmental pollutants in the subsurface aquatic environment harmful to human health and environment which are difficult to treat by traditional technologies Development of new technologies - Air stripping - Incineration - Biodegradation - Oxidation with chemicals - Carbon adsorption

3 SONOCEMICAL DEGRADATION OF ALOCOMPOUNDS AN OVERVIEW Development of new technologies (Advanced Oxidation Processes AOPs) Production of hydroxyl radical (O( O ) ) as a primary oxidant: -Photochemical treatment (UV, UV/ 2 O 2 ) -Ozonolysis -Fenton reaction Fe O 2 Fe(O) 2+ + O Application of ultrasound field is a successful tecnology for environmental clean-up Range of frequencies used kz

4 Ultrasound field SONOCEMICAL DEGRADATION OF ALOCOMPOUNDS AN OVERVIEW Physical effects (solution agitation) Cavitation (hight,p ) Chemical effects (solvent sonolysis) Pyrolytic degradation Radicals generation ))))) O 2 + O Pollutants oxidation O + O 2 O 2 + O 2 O 2

5 SONOCEMICAL DEGRADATION AN OVERVIEW Pyrolytic center ~ 5000 K 500 atm 2 O (g) O + S (g) products O + S (g) products Bulk solution T ~300K Interface T ~2000K O + S(aq) ) products S(aq) ) products 2O 2 O 2 O + S (aq) products 2 O 2(aq) + S (aq) products During the cavitational collapse of single, isolated bubbles,, extreme temperatures and pressures are achieved. The main chemical pathways for organic compound degradation include: - ydroxyl chemical oxidation - Direct pyrolytic degradation -Supercritical water reactions: Water vapor splits during bubble cavitation to yield and O Several organic compounds have been degradated using an ultrasonic field: - Aromatic compounds (phenol, chlorophenols) - Organic dyes - erbicides and pesticides - Aliphatic carboxilic acids - Surfactants

6 SONOCEMICAL DEGRADATION OF ALOCOMPOUNDS OBJECTIVES Study of the degradation of chlorinated organic compounds in aqueous solution using a 20 and 850 kz ultrasound field Degradation of perchloroethylene molecule in aqueous solution as a model Abbreviation Chemical name Comercial name Empirical formula PCE Tetrachloroethylene perchloroethylene, perc, C 2 C 2 Ethylene tetrachloride, tetrachloroethene,

7 Property Molecular weight Melting point Boiling point Density at 20ºC Solubility: Water at 25ºC Partition coefficients: Log K ow Log K oc Vapour pressure at 25ºC enry s law constant at 25ºC SONOCEMICAL DEGRADATION OF ALOCOMPOUNDS g/mol -19ºC 121ºC g/mL 150mg/L mm g 1.8 x 10-2 atm m 3 /mol Properties perchloroethylene Excellent solvent Applications azardous toxic compound US EPA Persistent pollutant Table of physical and chemical properties of perchloroethylene -Dry-cleaning industry -Metal cleaning -Vapor degreasing

8 SONOCEMICAL DEGRADATION EXPERIMENTAL PROCEDURE - Perchloroethylene (Aldrich 99%) used as received. -Solutions were prepared with purified water obtained from a Milli-Q system, 18.2 MΩ cm and previously deoxygenated by bubbling argon before addition n of pechloroethylene. - The solution was left stirring overnight. -Temperature was kept at 20 ±1 ºC with a refrigerated bath and circulator. -Ultrasonic irradiation was carried out at maximum volume (minimum headspace in the sonochemical reactor). -Samples were analyzed inmediately after collection

9 The degradation of perchloroethylene was studied by: Analysis of aqueous phase A) Following the chloride concentration formation in solution by Ion Exchange Chromatography B) Monitoring of PCE and byproducts by igh Performance Liquid Chromatograph (PLC) C) Detection and quantification of PCE and products from the degradation obtained at the end of each experiment was carried out using Purge and Trap Gas Chromatography Mass Spectrometry (PT-GC GC-MS) Analysis of gaseous phase SONOCEMICAL DEGRADATION A) Analysis CO/CO 2 by Gas Cromatographic with TCD (GC-TCD) B) Anaysis of PCE and intermediates by Gas Cromatographic with FID (GC-FID)

Cell dimensions: diameter 68mm depth 84mm Sonicated volume: : 200cm 3 (1) ultrasonic

10 SONOCEMICAL DEGRADATION Experimental set-up Sonoreactor ( Undatim) Frequency: : 20kz Maximum power output: 100W astelloy ultrasound horn: : 3 cm diam. Cell dimensions: diameter 68mm depth 84mm Sonicated volume: : 200cm 3 (1) ultrasonic probe (2) transducer (3) gas passing (4) electrolyte (5) cooling jacket (6) Teflon adaptor (7) O-ring joints.

11 SONOCEMICAL DEGRADATION Characterization of the sonoreactor,, 20kz, 100W 10 8 I/ W cm -2 Ultrasonic power input was measured using standard calorimetric procedures 6 4 Probe amplitude 20% Power dissipation in solution/ W 13 Acoustic intensity/ W cm Power density/ W ml -l % Amplitude/ % 60% 80% 100%

12 Initial concentration of PCE SONOCEMICAL DEGRADATION PCE concentration/ ppm [PCE]/[PCE] insonation time/min insonation time/min Concentration decay is uneffected by initial concentration of PCE [PCE] 0 = 14ppm [PCE] 0 = 64ppm [PCE] 0 = 100ppm 6.4 W cm -2 5h 20kz 20ºC

13 Ultrasonic intensity SONOCEMICAL DEGRADATION [PCE]/[PCE] W cm W cm W cm W cm W cm -2 The p was found to decrease in all cases due to the formation insonation time/min [PCE] 0 75ppm 20kz 5h 20ºC I/ W cm Yield of chloride formation/ %

14 Ultrasonic intensity SONOCEMICAL DEGRADATION k/ min log(c(t)/c(0) ,84 W cm -2 3,39 W cm -2 5,09 W cm -2 6,36 W cm -2 7,64 W cm I/ W cm t/ min Experimental results show that sonochemical destruction of PCE follows pseudo first-order kinetics

15 SONOCEMICAL DEGRADATION Main products from perchloroethylene sonochemical degradation: TCE Trans-DCE cis-dce C 2 3 trans-c cis-c Products detected by P&T-GC GC-MS after 5h: C 3 C 4 exachloroethane exachlorobutadiene exachloropropene

16 Ultrasonic intensity SONOCEMICAL DEGRADATION [PCE]/ ppm [TCE],[DCE],[ - ]/ ppm [PCE]/ ppm [TCE],[DCE],[ - ]/ ppm Sonochemical treatment leads to TCE and DCE and chloride anions as major by-products time/ min time/ min - - [PCE] - - [TCE] - - [DCE] - - [ - ] 1.84 W cm W cm -2

17 Mechanism: SONOCEMICAL DEGRADATION C )))))) C-C )))))) C- )))))) 2 C 2 + C C 3 x2 + + )))))) C- C 4 +

18 Experimental set-up SONOCEMICAL DEGRADATION Sonoreactor Meinhardt Ultraschalltechnik, K80-5 Frequency: 850kz Maximum power output: 140W Sonicated volume: 200cm ) Transducer,, 2) bulk solution,, 3) glass cell,, 4) sample withdrawing system,, 5) temperature probe,, 6) lid,, 7) inlet and outlet of the cooling jacket and 8) interface

19 SONOCEMICAL DEGRADATION Characterization of the sonoreactor,, 850kz, 140W Ultrasonic power output was measured using standard calorimetric procedures 50 power output Power input/ watts 2.2± ±0.1 W cm W cm ± amplitude 37.9±

20 SONOCEMICAL DEGRADATION Effect of PCE concentration Chloride conc/ ppm ppm perchloroethylene 75ppm perchloroethylene 38ppm perchloroethylene 150ppm PCE Saturation conditions!! [Chloride] final / ppm insonation time/ hours [PCE] initial / ppm yield perchloroethylene initial concentration/ ppm Initial Perchloroethylene Yield of - formation/ % concentration/ ppm

21 SONOCEMICAL DEGRADATION Effect of ultrasound power 6 0 Chloride concentration/ ppm w att 17 w att 5 w att 2 w att Yield of chloride formation / % Power output / Wh in s o n a tio n tim e / m in Ultrasonic power / watts Yield of - formation/ %

22 SONOCEMICAL DEGRADATION Products from perchloroethylene sonochemical degradation at tracer level: C 3 C 4 Mechanism?

23 SONOCEMICAL DEGRADATION CONCLUSIONS Perchloroethylene sonochemical degradation can be carried out Different behaviour has been detected with the frequency Sonochemical degradation seems mainly to follow a pyrolytic radical mechanism Total degradation can not be stablished from the results coming from - detection Differences in the by-products obtained with different frequencies are still under study

24 ACKNOWLEDGEMENTS Coventry University Generalidad Valenciana Finantial Support Alicante University COST D32/004 (Electrochemistry with Ultrasound)

25 Thank you!

Sonochemical Treatment of Water Polluted by Chlorinated Organocompounds. A Review

Water 2010, 2, 28-74; doi:10.3390/w2010028 OPEN ACCESS water ISSN 2073-4441 www.mdpi.com/journal/water Review Sonochemical Treatment of Water Polluted by Chlorinated Organocompounds. A Review José González-García